Remove support for the keygen tag

chrome/browser/resources/settings/site_settings/constants.js

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 cr.exportPath('settings');
 
 /**
  * All possible contentSettingsTypes that we currently support configuring in
  * the UI. Both top-level categories and content settings that represent
  * individual permissions under Site Details should appear here. This is a
  * subset of the constants found in site_settings_helper.cc and the values
  * should be kept in sync.
  * @enum {string}
  */
 settings.ContentSettingsTypes = {
   COOKIES: 'cookies',
   IMAGES: 'images',
   JAVASCRIPT: 'javascript',
   PLUGINS: 'plugins',
   POPUPS: 'popups',
   GEOLOCATION: 'location',
   NOTIFICATIONS: 'notifications',
   MIC: 'media-stream-mic',
   CAMERA: 'media-stream-camera',
   PROTOCOL_HANDLERS: 'register-protocol-handler',
   UNSANDBOXED_PLUGINS: 'ppapi-broker',
   AUTOMATIC_DOWNLOADS: 'multiple-automatic-downloads',
-  KEYGEN: 'keygen',
   BACKGROUND_SYNC: 'background-sync',
   USB_DEVICES: 'usb-chooser-data',
   ZOOM_LEVELS: 'zoom-levels',
 };
 
 /**
  * Contains the possible string values for a given contentSettingsType.
  * @enum {string}
  *
  * TODO(dschuyler): This should be rename as ContentSetting to maintain
@@ skipping 12 matching lines @@
  * A category value to use for the All Sites list.
  * @const {string}
  */
 settings.ALL_SITES = 'all-sites';
 
 /**
  * An invalid subtype value.
  * @const {string}
  */
 settings.INVALID_CATEGORY_SUBTYPE = '';